<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <style>
      .tail {
        margin: 100px auto;
        position: relative;
        width: 0;
        height: 0;
        border: 20px solid transparent;
        border-left: 20px solid red;
        transform: rotate(10deg);
      }
      .tail::before {
        content: "";
        position: absolute;
        border: 0 solid transparent;
        border-top: 10px solid red;
        border-radius: 20px 0 0 0;
        top: -8px;
        left: -69px;
        width: 50px;
        height: 15px;
      }
    </style>
  </head>
  <body>
    <p>弯道超车：先右边三角再旋转角度 使之倾斜；用before伪元素定位，给宽高 边框角度 和上边框 如果有需要再利用旋转调位置</p>
    <div class="tail"></div>
  </body>
</html>
